This invention relates to a method and apparatus for automatically inspecting and repairing simple matrix circuit panels. Inspection is achieved by electro-optic capacitance imaging, while repair is achieved by laser cutting and material deposition. The imaging process results in the generation of a list of panel defects, including the type and location of each defect. Automated repair then is performed by accessing such list to identify the defect type and location. Prescribed repair operations are performed based upon the type defect and location.
One specific application is for simple matrix LCD panels. Such panels are formed by a pair of transparent simple matrix panels coupled together. Each panel includes multiple, substantially parallel conductive lines typically formed with indium tin oxide ("ITO lines") or another transparent or translucent material. The two panels are coupled so that the lines on one panel are orthogonally oriented with respect to the lines on the other panel. To assemble the simple matrix LCD panel the two simple matrix panels are sandwiched together with liquid crystal injected between the panels. When lines on each panel become energized, the liquid crystal at an intersection point between the lines will change polarization in the liquid crystal material in proportion to the rms voltage differential so as to define a pixel.
Known methods for inspecting simple matrix panels for defects include optical inspection in which each panel is viewed to identify an area which does not conform to a particular appearance. Such a test, however, is not functional and does not determine with certainty that a defect in fact is present at such location.
Another method for inspecting is to perform resistance testing by applying probes to ITO lines. A simple matrix panel prior to assembly has alternating rows of ITO lines that are shorted to a shorting bar. The intermittent rows are left "open" without electrical coupling to a shorting bar. To perform the resistance testing, probes are coupled to the open ITO lines and grounded to the shorting bar. A signal then is applied to the probes. If any resistance is measured between the probes and ground, then a short circuit is present. Such a method, thus identifies whether a short circuit defect is present, but does not identify the location of the defect.
Accordingly, an improved testing (inspection) method is needed which can identify the presence and location of simple matrix panel defects with reliability.
For high density simple matrix LCD panels, for example, a typical yield of shipped panels is less than about 50% to 75%. Because of the significant percentage of defective panels, it is common to test all (100%) of the manufactured panels.
Accordingly, there is a need for an automatic system for identifying defects early in the manufacturing process to avoid further manufacturing steps for panels having a large number of defects. Further, there is a need for a method and apparatus for repairing panels having sufficiently few defects. In addition, there is a need for automating and linking the inspection and repair processes so as to increase the system throughput.